The present invention relates to polyamide layered films and more particularly to polyamide layered films suitable for packaging applications, which exhibit excellent sliding properties, transparency, and flex fatigue resistance, and which have good processing suitability in the step of printing or lamination when used as various packaging materials.
In the past, unstretched films or stretched films made of polyamide polymers, typical examples of which are nylon 6 and nylon 66, have been widely used as various packaging materials because they exhibit excellent strength and gas barrier properties as compared with films made of other ordinary polymers, thereby producing favorable effects; for example, they can prevent spoilage of contents when used as packaging materials for food packaging, particularly packaging of water-containing food, and furthermore, they can prevent package breaking that will be caused by vibration or shock during transportation.
The above conventional unstretched films or stretched films made of polyamide polymers have drawbacks that they can only exhibit poor sliding properties in a high humidity atmosphere and they may make many troubles, including printing failure or lamination failure, which will be caused by wrinkle generation in the processing step such as printing or lamination, so that workability cannot be improved at the time of film processing.
To solve the above drawbacks, there have been made many attempts, including addition of inorganic fine particles or organic lubricating agents in large quantities to polyamide polymer films, or application of a coating solution containing inorganic fine particles to polyamide polymer films, which, however, lead to deterioration of film transparency and complication of film producing processes, resulting in an increase in production cost; therefore, the above conventional unstretched films or stretched films made of polyamide polymers have not yet come to a satisfactory level.
Under these circumstances, the present inventors have extensively studied to solve the drawbacks of the above conventional unstretched films or stretched films made of polyamide polymers and to develop polyamide layered films suitable for packaging applications, which exhibit excellent film quality required for packaging films, including sliding properties, transparency, and flex fatigue resistance, and which have good processing suitability in the step of printing or lamination when used as various packaging materials, so that processing failure can be reduced and workability can be improved. As a result, they have found that such polyamide layered films can be obtained by formation of easy-sliding layers made of polyamide polymers containing specific amounts of inorganic fine particles and by control of static friction coefficient under specific conditions, thereby completing the present invention.
The present invention provides a polyamide layered film comprising a base layer made of a polyamide polymer and an easy-sliding layer made of a polyamide polymer containing inorganic fine particles at 0.15 to 3.00 wt %, the easy-sliding layer being formed on at least one surface of the base layer, and the first static friction coefficient between the easy-sliding layer side surfaces of the layered films at 23xc2x0 C. in a 65% RH atmosphere being 0.70 or lower.
This polyamide layered film can be effectively used as various packaging materials because they exhibit excellent film sliding properties, transparency, and flex fatigue resistance, and have good processing suitability in the step of printing or lamination, so that processing failure can be reduced and workability can be improved at the time of film processing.
The present invention further provides a polyamide layered film comprising a base layer made of a polyamide polymer and an easy-sliding layer made of a polyamide polymer containing 0.15 to 3.00 wt % inorganic fine particles, the easy-sliding layer being formed on at least one surface of the base layer, and the second static friction coefficient between the easy-sliding layer side surfaces of the layered films at 23xc2x0 C. in a 80% RH atmosphere being 0.95 or lower.
This polyamide layered film can be effectively used as various packaging materials because they exhibit excellent film sliding properties, transparency, and flex fatigue resistance, and have good processing suitability in the step of printing or lamination, so that processing failure can be reduced and workability can be improved at the time of film processing, particularly in a high humidity atmosphere.